We determined the reproducibility of measuring 24-hour sedentary total energy expenditure (STEE), sleep EE, and resting EE (REE) using a whole- room indirect calorimeter during two different occasions 6 weeks apart. We studied 61 prepubertal girls, mean age of 7.3 years (4.8-10.3 years) and a mean ideal body wt-for-ht of 106% (90-119%). The Pearson coefficient of correlation (r) and coefficient of variation (CV) were used to compare the STEE, sleep EE, and REE between the two visits for each child. Using paired t-tests, there were no significant differences in STEE, sleep EE, and REE on visits 1 and 2. The STEE, sleep EE, and REE on visits 1 and 2 were highly correlated, r of 0.76, 0.63, and 0.61, respectively. The CV in intra-individual STEE, sleep EE, and REE were 5.3%, 5.6%, and 7.7%, respectively. In conclusion, STEE, sleep EE, and REE measured in a whole-room indirect calorimeter in healthy, normal-weight prepubertal girls were highly reproducible.